1. Field of the Invention
The present invention relates to a drain mechanism and a fluid filter including the drain mechanism, and more particularly to a drain mechanism and a fluid filter including the drain mechanism with which a drain pipe can be inserted into a drain hole of a cap easily and with comparatively little force, and the drain pipe can be inserted straight and held securely.
2. Description of the Related Art
An oil filter having a drain mechanism for discharging oil remaining in the interior of a case during the replacement of a replaceable filter element is known as a conventional fluid filter (see Patent Document 1, for example).
As shown in FIG. 7, for example, Patent Document 1 discloses a drain mechanism 124 having a cap 103 that is attached detachably to a case of an oil filter 101 and formed with a drain hole 115, and a valve member 125 provided in the interior of the cap 103 so as to close the drain hole 115, in which the valve member 125 is pushed upward against the biasing force of a spring 111 by a tip end portion 134 of a drain pipe 133 inserted into the drain hole 115, thereby opening the drain hole 115 such that oil remaining in the interior of the cap 103 is discharged via the drain pipe 133. When the remaining oil is discharged, an engaging portion 135 of the drain pipe 133 is engaged with an engaging projecting portion 118 of the cap 103, and the tip end portion 134 of the drain pipe 133 is held in a holding recess portion 128 of the valve member 125. Thus, the drain pipe 133 is fixed to the cap 103.
Patent Document 1: Japanese Patent Application Publication No. JP-A-2005-111447
As shown in FIG. 8, however, with the drain mechanism 124 of Patent Document 1, when a tip end side of the engaging portion 135 of the drain pipe 133 inserted into the drain hole 115 is in contact with a rear end side of the engaging projecting portion 118 of the cap 103, an interval A′ between a contact tip end of the engaging portion 135 and the engaging projecting portion 118 and an open end of the holding recess portion 128 of the valve member 125 is set to be shorter than an interval B′ between the contact tip end of the engaging portion 135 and the engaging projecting portion 118 and a tip end of the drain pipe 133, and therefore, when insertion of the drain pipe 133 progresses further, as shown in FIG. 9, the engaging portion 135 and the engaging projecting portion 118 can only be engaged by subjecting the drain pipe 133 to excessive elastic deformation while the tip end portion 134 of the drain pipe 133 is housed and held within the holding recess portion 128. Hence, a comparatively large force is required to insert the drain pipe 133, and therefore the drain pipe 133 cannot be inserted easily. Furthermore, since the drain pipe 133 cannot be inserted easily, the drain pipe 133 may not be inserted into the drain hole 115 straight. As a result, the tip end portion 134 of the drain pipe 133 may not be housed completely in the holding recess portion 128 and may fall out.